Semiconductor heterostructures have been receiving attention in the art because of the added capabilities in device parameters that are made available to the device designer using these structures. As the art is developing, devices are appearing involving not only electrical conduction properties but also photoelectric conversion properties. Where both of these properties are employed in the same structure new considerations become involved in the operating regions of the device. For example, thicknesses of regions may effect not only carrier transport but also waveguide properties and transparency to light and a p-n junction may require not only electrical conduction front-to-back ratios but also the junction may require particularly good minority carrier diffusion adjacent thereto for optical efficiency. The semiconductor heterostructures and the techniques by which they have been fabricated have not yielded as great a control as the development of the art could use.